A rezhvolke is a satin overcoat worn by some Hungarian Hasidic Jews on Shabbos (the Jewish Sabbath). On Shabbos and Festivals-Hasidic men will wear a bekishe-a silk robe that replecates the kind worn in ancient Israel by the kohanim (tribal priests) who used to perform animal sacfrices to G-d in the Temple in Jerusalem. A rezhvolke is a coat worn over the bekishe-its a coat for the Sabbath. A Rabbi's rezhvolke will either have a silver or fur lining.

See related links below for a URL that shows a group of Hasidic men wearing their rezhvolkes. Notice the Rabbi's has a fur collar.

See related links below for a group of Hasidic men with just their bekishes, no rezhvolke-notice the difference (tied with a silk belt, no buttons, shinier appearance)

A rezhvolke is always work over a bekishe-never on its own-its gives the appearance of a very overweight person-but they're very thin, more comfortable then a regular business suit and such good quality silk that walking to synagogue in New York even gets cold in the deep of winter!

A Rabbi is always identifiable by his clothes-as I said, his rezhvolke has a velvet/fur lining and his bekishe either has a floral patter, or is solid white-the latter being the more traditional-but much less common due to its sensitivity to the modern, polluted urban air.

See related links below for a Rabbi's traditional white bekishe.